Scope
Scope refers to the
so-called
visibility
of identifiers within source code.
That is, given a particular identifier declaration, the
scope of the identifier determines where it is
legal to reference that identifier in code. For example, these two
functions each declare a variable CoffeeBreaks
.
Each declaration is invisible to the code in the other method. The
scope of each variable is the method in which it is declared.
Public Sub MyFirstMethod( ) Dim CoffeeBreaks As Integer ' ... End Sub Public Sub MySecondMethod( ) Dim CoffeeBreaks As Long ' ... End Sub
Unlike previous versions of Visual Basic, Visual Basic .NET has
block scope
. Variables declared within a set of
statements ending with End
,
Loop
, or Next
are local to that
block. For example:
Dim i As Integer For i = 1 To 100 Dim j As Integer For j = 1 To 100 ' ... Next Next ' j is not visible here
Visual Basic .NET doesn’t permit the same variable name to be declared at both the method level and the block level. Further, the life of the block-level variable is equal to the life of the method. This means that if the block is re-entered, the variable may contain an old value (don’t count on this behavior, as it is not guaranteed and is the kind of thing that might change in future versions of Visual Basic).
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